diff: fix crash with --find-object outside repository

When "git diff --find-object=<oid>" is run outside a git repository,
the option parsing callback eagerly resolves the OID via
repo_get_oid(), which reaches get_main_ref_store() and hits a BUG()
assertion because no repository has been set up.

Check startup_info->have_repository before attempting to resolve the
OID, and return a user-friendly error instead.

Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/diff.c b/diff.c
index 90e8003dd1..fd9aedbec7 100644
--- a/diff.c
+++ b/diff.c
@@ -5139,6 +5139,8 @@ static int diff_opt_find_object(const struct option *option,
 	struct object_id oid;
 
 	BUG_ON_OPT_NEG(unset);
+	if (!startup_info->have_repository)
+		return error(_("--find-object requires a git repository"));
 	if (repo_get_oid(the_repository, arg, &oid))
 		return error(_("unable to resolve '%s'"), arg);